This invention relates to exhaust gas return valves and in particular to actuating rods for interconnecting such a return valve with a throttle.
U.S. Pat. application Ser. No. 544,220, filed Jan. 27, 1975 now U.S. Pat. No. 3,989,018 by the present inventor, the disclosure of which is incorporated herein by reference, shows an exhaust gas control valve which is interconnected with a throttle by means of an actuating rod. Such an exhaust gas return valve is useful in motor vehicles for reducing nitrous oxide emissions. When a portion of the exhaust gas is returned to the intake manifold of an internal combustion engine the inert characteristics of the exhaust gas tend to reduce the peak combustion temperatures in the engine. This reduced combustion temperature results in a lower level of undesired nitrous oxide emissions.
As indicated in the prior patent application, it is desired that the portion of exhaust gases supplied to the intake manifold be varied in accordance with the throttle setting. The exhaust gas return valve has a closed position when the engine is idling, opens as the throttle is advanced and then closes again at full throttle against a stop. In order to permit full throttle actuation after the exhaust gas valve reaches its stop position, it is necessary to provide for resilient expansion of the actuating rod interconnecting the throttle with the exhaust gas valve. Resilient connection is also desirable in the event that the exhaust gas return valve becomes jammed on account of icing or contamination from exhaust gas deposits. By providng a resilient spring in the force transmitting direction of the actuating rod, it is possible to operate the throttle of the engine while the valve is jammed in a closed position.
The prior patent application discloses an actuating rod which provides resilient interconnection of the exhaust gas control valve and the throttle. The rod therein disclosed includes first and second rod portions which are in force transmitting interconnection by use of a spring. The first rod portion has a tubular section which is arranged coaxially around the second rod portion. The spring is arranged surrounding the tubular section. There is additionally provided an adusting nut, functioning as a turnbuckle which is useful for adjusting the length of the actuating rod and therfore the setting of the exhaust gas control valve.
While the actuating rod disclosed in the prior application is fully functional for its intended purpose, it is rather expensive to manufacture in large quantities for use on automobiles.